In current complex systems, the active components, ie. for the most part integrated circuits encapsulated in DIL packages, hybrid packages, flat packs, or chip carriers, etc. are soldered to printed circuit type supports known as "daughter cards" which are themselves interconnected by means of "mother cards". As a result there are chains of connection points, many of them soldered, thereby reducing reliability, particularly when operating conditions include vibrations and/or temperature changes.
Further, the components are generally soldered by means of their external connection points which means that these connection points are required to provide both electrical connection and mechanical connection which makes it difficult to test components since they cannot readily be removed from the card for testing or replacement.
Also, cooling is generally by convection, which may be natural or forced, and which generally uses air as the cooling fluid since liquids are generally not usable except in special circumstances such as using specially adapted circuit packages or in some kinds of ground-based equipment. Natural convection is not a very efficient cooling method, while forced convection has the drawback of polluting the circuits by rapidly covering them in dust.
Finally, since the systems concerned are complex, they are built up from a plurality of printed circuit cards which are themselves interconnected by other printed circuit or mother cards, thereby leading to relatively voluminous bulk, other things being equal. The current trend in electronics is away from bulky systems, and in some cases, eg. on board aircraft, electronic equipment must necessarily be compact, highly reliable in spite of vibrations, and readily disassembled for testing and component replacement where necessary. Since such systems are compact, they need effective cooling systems to remove the heat evolved during operation.
Preferred embodiments of the present invention provide the following advantages, inter alia:
a reduction in the number of interconnections;
the functions of interconnection, fixing, and packaging are separated, thereby improving reliability and facilitating maintenance;
reduced bulk; and
improved cooling.